The present invention relates to a disposable sensor used to measure properties, conditions and the other factors of fluid.
In many industrial and scientific fields, it is important to know properties of fluid such as specific gravity and coefficient of viscosity as well as conditions thereof such as temperature, flowing velocity and flow rate, and sensors of various types have already been proposed to measure such factors.
The inventors disclosed, for example, in Japanese Disclosure Gazette No. 1985-152943, a method for measuring changes in properties of liquid substance or semisolid substance, in which suitable metallic wire is supplied with electric current so that a temperature of the substance as well as a temperature of the metallic wire may be maintained at a predetermined value, simultaneously, a value of such electric current is measured and therefrom a heat transfer coefficient on the surface of the metallic wire is calculated to determine changes in the properties.
The inventors also disclosed, in Japanese Disclosure Gazette No. 1987-185146, a method for measuring conditions of fluid, in which temperatures of one or more sensor elements, a temperature of the fluid and differential temperatures between the respective sensor elements and the fluid are comparatively measured to determine conditions of the fluid. This Disclosure Gazette describes a stainless rod carrying platinum wire wound therearound and then coated with teflon, as a sensor used to perform this method.
It is also known, for example, from, Japanese Disclosure Gazette No. 1986-210959 to form a passage into which a liquid sample is introduced for detection of chemical ingredients thereof within this passage or for the like purposes and to assemble the passage and elements contained therein such as a detecting sensor and a pump into a disposable cartridge.
For properties, conditions and the other factors to be accurately measured, the surface of the sensor brought into contact with fluid to be measured must be free from any contamination.
However, in the well-known art as mentioned above, if said fluid to be measured comprises gelable substance, blood, detrimental substance for human body or the like, it will be difficult for such substance to be completely removed or washed away from the sensor when the sensor is not reused to prevent danger, or even when it is reused, even though the sensor is coated with teflon, and such inadequate washing will prevent the subsequent measurement from being accurately accomplished.
The sensor of said cartridge type contains therein various elements such as the pump and correspondingly, the cartridge itself becomes considerably expensive. With a consequence, the sensor of this type has usually been washed after every measurement and reused several times. Here again, however, washing of the sensor is difficult and troublesome, and the inadequate washing will often adversely affect the subsequent measurement. Thus, such sensor of cartridge type has left the problems of prior art unsolved.
Furthermore, a sensor for measurement of properties of fluid was generally expensive because of its complex mechanism, and the sensor was not suitable for disposable, essentially. The method of the present invention simplifies the structure of the sensor, and therefore, a practical disposable sensor can be constructed.